In the related art, there is a known light source device in which light beams output from a plurality of LED light sources and having different wavelengths are multiplexed and are introduced to an optical transmission rod, and the multiplexed light transmitted through the optical transmission rod is emitted (for example, see PTL 1). The light emitted from the light source device is made to enter an optical fiber cable in an endoscope and is used as illumination light.
In the light source device of PTL 1, part of the multiplexed light output from the optical transmission rod is extracted and is detected by a color sensor, and the color balance of the light beams from the respective LED light sources is adjusted by a color-balance circuit.